The field of the present invention is shredding machinery, particularly shredding machinery for converting paper, cardboard and other materials into a shredded form. While the structure disclosed and described hereinafter is primarily concerned with paper products and the like, similar structure of appropriate strength materials could be used for shredding metal or similar materials.
In previous U.S. Pat. Nos. 3,685,437 and 2,894,697, machinery is disclosed for the shredding of paper products and the like which is similar to that which is envisioned for use in connection with a shredder as hereinafter disclosed. In such a system, waste paper products are moved by a plurality of upwardly inclined successively overlapping conveyors each succeeding conveyor operating at a higher rate of speed than the one preceding it so as to cause the waste paper to be spacially dispersed in a longitudinal axial direction relative to the conveyor surface.
Although substantial spacial dispersion of waste paper products is accomplished in this fashion, the products tend to reaccumulate in the shredder to some extent and this is especially true when glops or wads of such products get conveyed into the shredder. The greater the potential exposure of the waste paper products to moisture becomes as the result of acquiring, storing and transporting it to the shredder, the more likely it is that glops or wads will form. The result may be that the shredder forcibly slows or jams and the shredding apparatus which includes electromechanically rotated shredding structure is inhibited in or prevented from operating. Several serious results can result from this phenomenon. First, resistance can build up in the electric motor driving the apparatus or in the control system for the motor or both and if safety shut offs are not installed or if installed are not quickly functional, either the motor or controls or both may burn out. If safety shut off controls operate or the motor or controls burn out delays of the shredding operation result for potentially substantial periods of time. Second, journal and bearing structure for one or more shafts involved in the operation of the structure may be severely damaged resulting in even longer periods of machine shut down time while repairs are made.
Since the shredded material is simply being baled for shipment to a center for reprocessing, it is not that critical that every glop or wad be that thoroughly shredded and some may even pass through the shredder virtually unscathed and still be included in the bale. One important reason for this is that the shredded material is often reprocessed into paper or cardboard by being dumped into vats where water and chemicals are added to further break the waste down in the reprocessing process.
It is desirable, therefore, to provide in structure of the character described, a shredder constructed and controlled to eliminate the problems above described.